The main tasks of geodetic astronomy are the determination of geographic latitude, geographic longitude and azimuth of terrestrial direction from observation of celestial bodies, i.e. from astronomic observations. Closely connected with the determination of geographic longitude is determination of time. It is known that geographic longitude is the difference between local and Greenwich time. Determination of time as an independent task is being performed by time services that connect their quartz and atomic clocks to astronomic observations and emit the obtained time through time-signals.